The present invention is directed to character displays in which the characters are formed of segments each of which can be selectively activated by connection to an external source of voltage. More particularly, the present invention is concerned with such character displays in which the character is formed of the segments described on one of a pair of plates, the other of the pair of plates having on the surface thereof pairs of common electrodes, each pair of common electrodes being opposed to a character on said one plate. The desired display pattern is displayed through the use of a dielectric material such as liquid crystal between the plates, PLZT, or electrochromic material between the plates. It is only necessary that the dielectric material change in appearance in response to the imposition of an electric field.
In the usual seven-segment assembly for displaying numerals, the seven segments are on one plate and a common electrode is disposed on the other plate forming a cell with said one plate. This arrangement requires a total of eight leads for displaying a single digit. Where a plurality of rows of digits or other characters is to be displayed, the number of leads becomes inconveniently great from two standpoints. The first of these is that a large fraction of the display area must be devoted to leads from the edge of the plate to the separate segments and to the common electrode. In addition, mass production becomes difficult since the leads must be disposed with great accuracy in order to avoid either open circuits or short circuits.
With the objective of decreasing the number of leads necessary for displaying a single digit, arrangements of the segment have been developed in which the segments on the one plate are grouped. The facing electrode on the other plate is then divided into two common electrodes rather than the usual one common electrode. A multiplexing technique makes it possible to display any of the numerals from 0 to 9 through the use of only four leads on the one plate and two leads on the other, such an arrangement therefore operating with only six leads per digit.
While the number of leads necessary for display of a digit or other characters is reduced through the use of two common electrodes rather than one, nevertheless, trunk lines with branch lines leading to each of the common electrodes must be provided. Moreover, the arrangement of the trunk lines must be such that no part of a trunk line opposes a lead line on the facing plate since, if there is such opposition, the region of the plate where the opposition occurs will become visible, and confusion will result. Consequently, an arrangement in which the space required for trunk lines is decreased and which avoids the possibility of an undesired opposition between trunk lines on one plate and lead lines on the facing plate where the characters are arranged in at least two rows or columns is to be desired.